added test cases and rez env flag

Signed-off-by: Ben Andersen <ben@isohedron.com.au>

src/rez/cli/env.py

@@ -116,6 +116,10 @@ def setup_parser(parser, completions=False):
     parser.add_argument(
         "--no-pkg-cache", action="store_true",
         help="Disable package caching")
+    parser.add_argument(
+        "--pkg-cache-sync", action="store_true",
+        help="Disable asynchronous package caching.  "
+             "Process will block until packages are cached.")
     parser.add_argument(
         "--pre-command", type=str, help=SUPPRESS)
     PKG_action = parser.add_argument(
@@ -212,7 +216,8 @@ def command(opts, parser, extra_arg_groups=None):
             caching=(not opts.no_cache),
             suppress_passive=opts.no_passive,
             print_stats=opts.stats,
-            package_caching=(not opts.no_pkg_cache)
+            package_caching=(not opts.no_pkg_cache),
+            package_cache_async=(not opts.pkg_cache_sync),
         )
 
     success = (context.status == ResolverStatus.solved)

src/rez/package_cache.py

@@ -366,7 +366,7 @@ def remove_variant(self, variant):
 
         return self.VARIANT_REMOVED
 
-    def add_variants(self, variants, _async=True):
+    def add_variants(self, variants, package_cache_async=True):
         """Update the package cache by adding some or all of the given variants.
 
         This method is called when a context is created or sourced. Variants
@@ -460,18 +460,14 @@ def add_variants(self, variants, _async=True):
                 else:
                     out_target = devnull
 
-                func = subprocess.Popen
-
-                # use subprocess.call blocks where subprocess.Popen doesn't
-                if not _async:
-                    func = subprocess.call
-
-                func(
+                process = subprocess.Popen(
                     args,
                     stdout=out_target,
                     stderr=out_target,
                     **kwargs
                 )
+                if not package_cache_async:
+                    process.wait()
 
         except Exception as e:
             print_warning(

src/rez/resolved_context.py

@@ -167,7 +167,7 @@ def __init__(self, package_requests, verbosity=0, timestamp=None,
                  package_filter=None, package_orderers=None, max_fails=-1,
                  add_implicit_packages=True, time_limit=-1, callback=None,
                  package_load_callback=None, buf=None, suppress_passive=False,
-                 print_stats=False, package_caching=None):
+                 print_stats=False, package_caching=None, package_cache_async=None):
         """Perform a package resolve, and store the result.
 
         Args:
@@ -205,6 +205,8 @@ def __init__(self, package_requests, verbosity=0, timestamp=None,
             package_caching (bool|None): If True, apply package caching settings
                 as per the config. If None, enable as determined by config
                 setting :data:`package_cache_during_build`.
+            package_cache_async (Optional[bool]): If True, cache packages asynchronously.
+                If None, use the config setting :data:`package_cache_async`
         """
         self.load_path = None
 
@@ -249,6 +251,10 @@ def __init__(self, package_requests, verbosity=0, timestamp=None,
 
         self.package_caching = package_caching
 
+        if package_cache_async is None:
+            package_cache_async = config.package_cache_async
+        self.package_cache_async = package_cache_async
+
         # patch settings
         self.default_patch_lock = PatchLock.no_lock
         self.patch_locks = {}
@@ -1846,7 +1852,7 @@ def _update_package_cache(self):
         if pkgcache:
             pkgcache.add_variants(
                 self.resolved_packages,
-                config.package_cache_async
+                self.package_cache_async
                 )
 
     @classmethod

src/rez/rezconfig.py

@@ -279,7 +279,8 @@
 package_cache_during_build = False
 
 # Enable package caching to run asynchronously during a resolve.
-package_cache_async = True 
+# If this is false, a resolve will block until all packages are cached.
+package_cache_async = True
 
 # Allow caching of local packages. You would only want to set this True for
 # testing purposes.
@@ -316,7 +317,7 @@
 # This is useful as Platform.os might show different
 # values depending on the availability of ``lsb-release`` on the system.
 # The map supports regular expression, e.g. to keep versions.
-# 
+#
 # .. note::
 #    The following examples are not necessarily recommendations.
 #
@@ -1122,7 +1123,7 @@
 
 # Enables/disables colorization globally.
 #
-# .. warning:: 
+# .. warning::
 #    Turned off for Windows currently as there seems to be a problem with the colorama module.
 #
 # May also set to the string ``force``, which will make rez output color styling

src/rez/tests/test_package_cache.py

@@ -134,7 +134,6 @@ def test_caching_on_resolve(self):
 
             # Creating the context will asynchronously add variants to the cache
             # in a separate proc.
-            #
             c = ResolvedContext([
                 "timestamped-1.2.0",
                 "pyfoo-3.1.0"  # won't cache, see earlier test
@@ -144,14 +143,64 @@ def test_caching_on_resolve(self):
 
         # Retry 50 times with 0.1 sec interval, 5 secs is more than enough for
         # the very small variant to be copied to cache.
-        #
         cached_root = None
+        resolve_not_always_cached = False
         for _ in range(50):
-            time.sleep(0.1)
             cached_root = pkgcache.get_cached_root(variant)
             if cached_root:
                 break
 
+            resolve_not_always_cached = True
+            time.sleep(0.1)
+
+        self.assertNotEqual(cached_root, None)
+
+        # Test that the package is not immediately cached, since it is asynchronous
+        # WARNING: This is dangerous since it does open the test to a race condition and
+        #   will fail if the cache happens faster than the resolve.
+        self.assertNotEqual(resolve_not_always_cached, False)
+
+        expected_payload_file = os.path.join(cached_root, "stuff.txt")
+        self.assertTrue(os.path.exists(expected_payload_file))
+
+        # check that refs to root point to cache location in rex code
+        for ref in ("resolve.timestamped.root", "'{resolve.timestamped.root}'"):
+            proc = c.execute_rex_code(
+                code="info(%s)" % ref,
+                stdout=subprocess.PIPE,
+                universal_newlines=True
+            )
+
+            out, _ = proc.communicate()
+            root = out.strip()
+
+            self.assertEqual(
+                root, cached_root,
+                "Reference %r should resolve to %s, but resolves to %s"
+                % (ref, cached_root, root)
+            )
+
+    @install_dependent()
+    def test_caching_on_resolve_synchronous(self):
+        """Test that cache is updated as expected on
+        resolved env using syncrhonous package caching."""
+        pkgcache = self._pkgcache()
+
+        with restore_os_environ():
+            # set config settings into env so rez-pkg-cache proc sees them
+            os.environ.update(self.get_settings_env())
+
+            # Creating the context will synchronously add variants to the cache
+            c = ResolvedContext([
+                "timestamped-1.2.0",
+                "pyfoo-3.1.0",
+                ],
+                package_cache_async=False,
+            )
+
+        variant = c.get_resolved_package("timestamped")
+        # The first time we try to access it will be cached, because the cache is blocking
+        cached_root = pkgcache.get_cached_root(variant)
         self.assertNotEqual(cached_root, None)
 
         expected_payload_file = os.path.join(cached_root, "stuff.txt")